Bearing system for balance knife edges and scale pivots

ABSTRACT

A bearing system comprising two or more cylindrical bearing members positioned in tandem relation and having the axes thereof extending parallel to, but offset from, each other for supporting a knife edge or pivot therebetween. Support means for the bearing members is disclosed which permits limited pivotal movement of the bearing members to provide uniform support over the entire length of the knife edge.

' United States atent 11 1 11 3,727,995 Ruefenacht Apr. 17, 1973 [5BEARING SYSTEM FOR BALANCE 1,583,251 4/1926 Hein ..308/2 R KNIFE EDGESAND SCALE PIVOTS 2,387,202 1 il i s.

2,013,539 9/1935 Gilbert [76] inventor: Werner Russell Ruefenacht, 26 5O3,387,898 6/1968 Hadley South West Temple, Salt Lake 3,401,964 9/1968Johnson ..30s/72 Utah 84115 Sept Primary Examiner-Charles Myhre Appl.No.: 177,057

Assistant Examiner-R. H. Lararus Attorney-Lynn G. Foster [57] ABSTRACT Abearing system comprising two or more cylindrical bearing memberspositioned in tandem relation and having the axes thereof extendingparallel to, but offset from, each other for supporting a knife edge orpivot therebetween. Support means for the bearing members is disclosedwhich permits limited pivotal movement of the bearing members to provideuniform support over the entire length of the knife edge.

4 Claims, 10 Drawing Figures PATENTEDAPRIYIQB 3,727,995

' snmlurz IN VENTOR.

co a WERNER RUSSELL RUEFENACHT I ATTORNEY PATENTED APR 1 71973 SHEET 2OF 2 INVENTOR. WERNER RUSSELL RUEFENACHT ATTORNEY BEARING SYSTEM FORBALANCE KNIFE EDGES AND SCALE PIVOTS BACKGROUND 1. Field oflnventionThis invention relates to bearings and is particularly directed tobearing systems for balanced knife edges and scale pivots, as areemployed in weighing devices and the like.

2. Prior Art The manufacture of weighing devices, such as balances andscales, is probably one of the oldest arts known to man. Throughout thehistory of this art, there has been a ceaseless quest for greateraccuracy which, in turn, has led to a continuing search for improvedbearing systems. The use of knife edges has long been conventional forprecision balances and scales. However, the search has continued forimproved surfaces upon which the knife edges must bear. Up to thepresent time, knife edges were made to bear on flat, grooved, orV-shaped bearings. The grooved or V- shaped bearings have beenparticularly employed in situations wherein it is important to attemptto maintain the oscillating balance or scale beam in alignment with thebalance or scale as a whole; for example, where optical readoutmechanisms are employed. However, such grooved or V-shaped bearings aredifficult to finish to a fine bearing surface. Moreover, the Vshapedbearings, if finely finished to close tolerances, prevent oscillation ofthe knife edge or pivot due to the tight fit, or, if not finelyfinished, fail to completely maintain the alignment of the oscillatingmember because of lack of close tolerances. Grooved bearings also do notcompletely maintain the alignment.

BRIEF SUMMARY AND OBJECTS OF THE INVENTION These disadvantages of theprior art are overcome with the present invention and a novel bearing isprovided which completely maintainsthe alignment of the oscillatingmember while providing substantially friction-free support uniformlyalong the entire length of edge or pivot.

In accordance with the present invention, a novel bearing system isprovided which presents essentially a low friction line bearing surfaceto the knife edge, yet is relatively inexpensive to produce, and isself-adjusting to maintain the knife edge in alignment with the weighingdevice as a whole.

The advantages of the present invention are preferably attained byproviding a bearing system comprising two or more spaced cylindricalbearing members wherein the bearing members are mounted with thelongitudinal axes thereof extending substantially parallel to, butslightly offset laterally from, each other. The bearing members of eachpair are secured in a manner such that they each have a limited amountof freedom to permit self-adjustment to the knife edge.

Accordingly, it is an object of the present invention to provideimproved bearing systems for weighing devices and the like.

Another object of the present invention is to provide improved bearingsurfaces for use in knife edge beam balances, scales and the like.

A further object of the present invention is to provide a bearing systemfor knife edges which is selfadjusting to the lay of the knife edge.

An additional object of the present invention is to provide improvedbearing surfaces for maintaining an oscillating member in alignment withthe weighing device as a whole.

A specific object of the present invention is to provide a bearingsystem for knife edges comprising two or more spaced cylindrical bearingmembers wherein each bearing member is mounted with its longitudinalaxis extending substantially parallel to, but slightly offset laterallyfrom, each other bearing member and wherein each bearing member issecured in a manner such that it has a limited amount of freedom topermit self'adjustment to align itself with the knife edge.

These and other objects and features of the present invention will beapparent from the following detailed description, taken with referenceto the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an isometric view of a knifeedge bearing system embodying the present invention, with parts brokenaway for clarity;

FIG. 2 is an end view of the bearing system of FIG. 1, with parts brokenaway for clarity;

FIG. 3 is a side view of the bearing surface of the I bearing system ofFIG. 1;

FIG. 4 is an isometric view of a modified form of the bearing surface ofthe bearing system of FIG. 1;

FIG. 5 is a horizontal section through the bearing surface of FIG. 4,taken on the line 5-5 thereof;

FIG. 6 is a transverse section through the bearing surface of FIG. 4,taken on the line 6-6 thereof, with parts broken away for clarity; and

FIGS. 710 are diagrammatic representations showing the freedom ofmovement of the bearing members of the bearing system of FIG. 1 whensubjected to restrain at respective points.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENT In that form of thepresent invention chosen for purposes of illustration in FIG. 1, abearing system, indicated generally at 2, comprises a knife edge 4supporting a balance arm 6, or the like, engaging a bearing surface,indicated generally at 8, formed by a pair of cylindrical bearingmembers 10 and 12. It will be apparent that, if desired, more than twotandem bearing members could be employed. However, for purposes ofbrevity, the following description refers to two bearing members only.The bearing members 10 and 12 are mounted in respective recesses 14 and16 formed in the opposite arms 18 and 20 of a generally U-shaped support22. A second, generally U-shaped member 24 has upwardly extending arms26 and 28 which extend adjacent the free ends 30 and 32 of the bearingmembers 10 and 12 to permit limited axial movement of the bearingmembers 10 and 12.

As best seen in FIGS. 2 and 3, the bearing members 10 and 12 are mountedin tandem with the longitudinal axes thereof extending parallel to, butoffset from, each other. The arms 18 and 20 of support 22 engage thebearing members 10 and 12 midway of the length of the bearing members 10and 12'and recesses 14 and 16 are formed generally circular and aredimensioned to provide a sliding fit with the bearing members 10 and 12.As shown, the recesses 14 and 16 follow the periphery of the bearingmembers 10 and 12 to a point well above the horizontaldiameter of thebearing members 10 and 12 and, hence, provide both vertical and lateralrestraint of the bearing members 10 and 12. However, the recesses 14 and16 are open at the upper ends thereof and the bearing members 10 and 12project slightly beyond the upper ends of the recesses 14 and 16 toprovide uninterrupted engagement with the knife edge 4. As best seen inFIGS. 1 and 3, the knife edge 4 extend parallel .to the axes of thebearing members 10 and 12 and is supported by the upper surfaces of thebearing members 10 and 12. It will be apparent that, as seen in FIG. 2,bearing member 10 engages only the right side of knife edge 4 and,hence, urges knife edge 4 toward the left, while bearing member 12engages only the left side of knife edge 4 and, thus, urges knife edge 4toward the right. This provides a force couple which tends to rotateknife edge 4. However, this tendency is compensated by providing asecond bearing system, not shown, which is identical to bearing system 2but is spaced therefrom along knife edge 4. Obviously, knife edge 4 neednot be continuous betweenthe two bearing systems, provided that theknife edges of the two spaced bearing systems are colinear. In thisinstance, the force couples provided by the bearing systems willcompensate through the balance arm 6. On the other hand, it will be seenthat the pressure of knife edge 4 is applied substantially tangentiallyalong the length of each of the bearing members 10 and 12.

Referring to FIG. 8, momentarily, it has been pointed out above, thatrecesses 14 and 16 and arms 18 and 20 of support 22 serve to restrainvertical and lateral movement of the midpoints of bearing members 10 and12. This restraint isreprese'nted, in FIG. 8, by arrows) ing members 10and 12. Obviously, axial-movement of either of the bearing members 10 or12 away from arms 26 and 28 will be limited by engagement with'the otherbearing member 12 or 10. However, this limited axial movement, coupledwith the centrally applied vertical and lateral restraint, representedby arrows 34, permits each of the bearing members 10 and 12 to' pivotabout its midpoint, as indicated by arrows 36, and to rotate about itsaxis, as indicated by arrow 38. Thus, each of the bearing members 10 and12 enjoys considerable freedom of movement and, thus, can readilyaccommodate movement of knife edge 4 without varying the alignment ofthe knife edge 4.

FIGS. 4, and 6 illustrate a modified formof the bearing surface 8 of thepresent invention. In this form of the invention, a bearing supportblock 40 is provided. The upper surface 42 of support block 40 is formedwith a pair of intersecting recesses 44 and 46 conforming substantiallyto the shape and desired orientation of the bearing members and 12,which are identical to those of FIGS. 1-3. A pair of screws 48, carryingwashers 50, are secured to the block 40 and overlap the recesses 44 and46 to provide limited axial movement of the bearing members 10 and 12. Alongitudinal bore 52 communicates with recess 44 and extend from one endof block 40 to a. point slightly beyond the recess 44, thereby providinga horizontal recess 54 communicating with recess 44. Similarly, a secondlongitudinal bore 56 communicates with recess 46 and extends from oneend of block 40 to a point slightly beyond recess 46, thereby providinga horizonm1 recess 58 communicating with recess 46. In addition,vertical recesses communicating with the recesses 44 and 46 areprovided, as seen at 60 in .FIG. 6. A plurality of spheres 62 areprovided, each located in a respective one of the recesses 54, 58 and 60and are dimensioned so as to project slightly into the adjacent recess44 or 46. The recesses 44 and 46 are of slightly greater diameter thanthe bearing members 10 and 12 and, hence, serve to provide vertical andlateral restraint for the bearing members 10 and 12. However, spheres 62provide point supports for the bearing members 10 and 12 so that thebearing members 10 and 12 are free to pivot about the spheres 62 insubstantially the manner described with; respect to FIG. 8. If desired,cylindrical or polygonal shaped members may be substituted for thespheres 62, so long as they provide point support for the bearingmembers 10 and 12.

FIGS. 7, 8, 9 and 10 represent alternative manners in which the bearingmembers 10 and 12 may be restrained, while providing pivotal freedom ofmovement, as previously described with'respect to FIG. 8, to accommodatevariations in the pressure applied by the knife edge and the manner inwhich suchpressure is applied. As seen in'FIG. 7, restraints are appliedto the adjacent ends of bearing members 10 and 12, as indicated byarrows 64 and 66, respectively, while the opposite ends of the bearingmembers 10 and 12 are free to pivot, as indicated by arrows 68 and 70,respectively. In FIG. 9, the adjacent ends of the bearing members 10 and12 are free to pivot, while the opposite ends thereof are restrained, asindicated'by arrows 72 and 74, respectively. In FIG. 10, theproximal-end of each of the bearing members 10 and 12 are restrained, asindicated, respectively, by arrows 76 and 78, while the distal ends ofeach of the bearing members 10 and 12 are free to pivot.

- Obviously, numerous variations and modifications may be madewithoutdeparting'from the present invention. Accordingly, it should beclearly understood that the forms of the present invention describedabove and shown in the accompanying drawings are illustrative only andare not intended to limit the scope of the invention.

What is claimed is:

l. A bearing system comprising: at least two of cylindrical bearingmembers disposed in tandem relation and having the axes thereofextendingessentially parallel to, but laterally dis-' cylindrical bearing membersand to said point support means along said knife edge axis in adirection substantially normal thereto causing yaw axial reorientationof the cylindrical bearing members until the axis of each is preciselyparallel to the ad-' jacent knife edge axis. 2. The bearing system ofclaim 1 wherein said support means comprises:

a generally U-shaped supporthaving the upwardly extending arms thereofrespectively engaging said bearing membersalong one radial location eachsubstantially midway of the length of the contiguous bearing member andreceiving each said bearing member in. a generally circular open--topped recess formed in said respective arms.

x 3. The bearing system of claim 1 wherein said point support meanscomprises:

' point support members positioned in each of said horizontal andvertical recesses and projecting into said open-topped recesses toengage the adjacent cylindrical bearing member.

4. The bearing system of claim 1 wherein said point support meanscomprise spheres.

1. A bearing system comprising: at least two of cylindrical bearingmembers disposed in tandem relation and having the axes thereofextending essentially parallel to, but laterally displaced from, eachother, first and second point support means contiguous with each saidcylindrical bearing members to which the load from said contiguouscylindrical bearing is transferred, each point support means permittinglimited yaw axial reorientation of said contiguous bearing members, anda knife edge member having an axis essentially parallel to andintermediate of the axes of the cylindrical bearing members and imposinga load on said cylindrical bearing members and to said point supportmeans along said knife edge axis in a direction substantially normalthereto causing yaw axial reorientation of the cylindrical bearingmembers until the axis of each is precisely parallel to the adjacentknife edge axis.
 2. The bearing system of claim 1 wherein said supportmeans comprises: a generally U-shaped support having the upwardlyextending arms thereof respectively engaging said bearing members alongone radial location each substantially midway of the length of thecontiguous bearing member and receiving each said bearing member in agenerally circular open-topped recess formed in said respective arms. 3.The bearing system of claim 1 wherein said point support meanscomprises: a block having open-topped recesses formed in the uppersurface thereof receiving said bearing members and conformingsubstantially to the shape and desired orientation of said bearingmembers but of slightly greater diameter than said bearing members,horizontal and vertical recesses formed in said block and communicatingwith said open-topped recesses, and point support members positioned ineach of said horizontal and vertical recesses and projecting into saidopen-topped recesses to engage the adjacent cylindrical bearing member.4. The bearing system of claim 1 wherein said point support meanscomprise spheres.